Entheseal Changes and Functional Implications of the Humeral Medial Epicondyle

Abstract

Longitudinal rotation of the forearm (pronosupination) is an essential component of human manipulative tasks. The efficiency of this movement is dependent not only on the rotatory muscles but also on several morphological and structural features of the upper limb. In a recent study, we observed that the size and orientation of the humeral medial epicondyle played an important role in forearm rotatory ability. We further observed that the forearm muscular activity, specifically the motion of pronation, promotes radial curvature, which, in turn, enhances rotational efficiency. In this study, we aim to test whether the orientation of the medial epicondyle is an activity‐dependent parameter or whether it is an invariable morphological feature characteristic of the human skeleton. We analysed the upper limb entheseal changes in 30 human skeletons and assessed the role of several functional groups in the anteroposterior and proximo‐distal orientation of the medial epicondyle. Our results indicate that the orientation of the medial epicondyle is partially an activity‐dependent feature basically determined by elbow flexor‐extensors and hand and wrist flexors. The orientation of the medial epicondyle towards more posterior and proximal positions causes a gain of efficiency in the pronation range when the elbow is extended and in the supination range when the elbow is flexed. Therefore, we suggest that the medial epicondyle of the humerus is a structure involved in the manipulative capacities of the human upper limb, and its orientation presents a range of variation that may be associated with the functional enhancement of these abilities. Copyright © 2012 John Wiley & Sons, Ltd.

Special Issue Entheseal Changes and Occupation: Technical and Theoretical Advances and Their Applications

“…Although these papers emphasise important considerations and new methods, they are less theoretical than those in the previous sections and show a more practical use of EC. The first paper in this section (Ibáñez‐Gimeno et al , ) tests the relationship between pronosupination, as measured by the orientation of the humeral medial epicondyle and EC, to determine whether the orientation of this feature can be used as a marker of activity. The results found that the angle of the medial epicondyle increases the efficiency of the pronation range when the elbow is extended.…”

Biomechanics of Forearm Rotation: Force and Efficiency of Pronator Teres

“…A more posteriorly oriented epicondyle, i.e. more retroflexed [5] , [30] , is associated with a greater E rot in full extension of the elbow, whereas an epicondyle with a lower degree of retroflexion has greater values of E rot in full flexion. Moreover, a more proximally oriented epicondyle enhances E rot in full flexion, whereas when it is more distally oriented, E rot increases in extension.…”

“…Moreover, a more proximally oriented epicondyle enhances E rot in full flexion, whereas when it is more distally oriented, E rot increases in extension. The orientation of the medial epicondyle was reported to present a partially activity-dependent plasticity, and so it was hypothesized that it can be modified to enhance certain abilities [30] . In this regard, and in agreement with the abovementioned relationship between E rot and epicondylar orientation, a simple observation of the upper-limb positioning shows that a habitual and continued contraction of PT in full elbow flexion would reorient the epicondyle towards a more proximal position.…”

New Insights into Activity-Related Functional Bone Adaptations and Alterations in Neolithic Liguria (Northwestern Italy)

“…The shape of the humeral medial epicondyle appears to have an influence on the pronationsupination range during elbow flexion and extension [115] . Among Upper Palaeolithic hunters, throwing has also been considered to be one of the main factors determining the remarkable degree of asymmetry in humeral mechanical rigidity, which is comparable or greater than that shown in professional tennis players or, indeed, throwers (e.g.…”